Mortar sight



e J. E.. DARR, JR., ET AL Aug. 16, 194,9.

MORTAR S IGHT 5 Sheets-Sheet l Filed Dec. l1, 1945 Aug. 16, 1949. J. E. DARR, JR., ET AL v 2,478,898

' MORTAR SIGHT Filed Dec. 11, 1945 5 Sheets-Sheet 2 Aug. 16, 1949. .1. E. DARR, JR., ET Al. l 2,478,898

MORTAR SIGHT 3 Sheets-Sheet 5 Filed Dec. ll, 1945 Patented Aug. 16, 1949 MORTAR SIGHT John E. Darr, Jr., Arlington, Va., and William U. Matson. Takoma Park, Md., assignors to the United States of America as represented by the Secretary of War Application December 11, 1945, Serial No. 634,325

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 15 Claims.

The invention described in the following specication and claims may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to a sight for mortars. A mortar is an artillery weapon having a relatively short, smooth-bore barrel with a shorter range than a howitzer of equal bore and intended for use at higher angles of re to reach targets that are protected or concealed by intervening hills or other short-range barriers. While the :tire from such weapons is essentially less accurate than that from a gun or howitzer, the relatively long trajectories of the high angles of re generally used, make it important that the weapon be elevated accurately to the angle corresponding to the range of the target that it is desired to hit. It is also highly desirable that, except for minor corrections for windage, the mortar be aimed so that its bore axis lies in the plane determined by the mortar, target and the vertical. Other factors which are important in sights for weapons of this character are ease and rapidity of attachment and detachment, ease and certainty of accurate elevation under all conditions of visibility, the rapidity with which the sight, once adjusted, maybe used to accurately lay the weapon and the simplicity and sturdiness of construction.

It is therefore an object of the invention to provide a combined sight and elevating quadrant for mortars that may be quickly attached and detached by means of a special mounting bracket.

A further object is to provide a sight wherein the proper angle of elevation and azimuth angle of the mortar may be determined substantially simultaneously by a single operator who may, at the same time note whether or not the axis of the bore lies in the aforesaid vertical plane.

Another object is to provide an elevation quadrant carrying a line of sight device and so constructed that adjustments for elevation to the nearest degree may be made by sound or feel when operating under conditions of poor visibility, and without the necessity for counting individual degrees of angular adjustment.

A still further object is to provide a mortar sight that is relatively simple, easy, and inexpensive to construct while, at the same time, providing a sight and elevation quadrant having the necessary sensitivity for the Weapon with which it is to be used.

Yet another Vobject is to provide a sight for mortars that is rugged and capable of withstanding the severe shocks 9i ,f rlg, while at the same time easily repaired by the rapid substitution of interchangeable repair parts.

Other objects and advantages will become apparent as the description advances.

In the drawings:

Figure 1 shows a side elevation of the improved sight attached to a mortar barrel and showing the sight set for zero quadrant elevation.

Figure 2 is a section taken upon a plane indicated by the line 2--2, Figure 1 and showing the elevation quadrant, the quick-detachable mounting, and the sight set for zero quadrant elevation.

Figure 3 is a bottom plan view of the sight. quadrant and mounting bracket in place upon the mortar barrel.

Figure 4 is a sectional view taken upon a plane indicated by the line 4-4 of Figure 1 and showing more particularly the pivot and clamping means for the sight arm, the' quick detachable bracket mounting and one of the ball detent sight depression determining means,

Figure 5 is a development of a section taken upon the curved line 5-5 of Figure 1, showing the -manner in which a plurality of teeth upon the sight arm engage with corresponding teeth upon the elevation quadrant to positively lock the arm in adjusted position.

Figure 6 is a section taken upon the line 6-6, Figure 4, showing the details of the connection between the two parts of the mounting bracket and the connection of one part to the quadrant,

Figure 7 is a perspective view of that part of the mounting bracket attached to the quadrant.

Figure 8 is a perspective view of that part of the mounting bracket attached to the mortar clamp,

Figure 9 is a perspective view of the retaining spring and its integral mounting plate,

Figure 10 is a sectional detail of the level vial, mirror, and their mounts, taken upon the line lli-I0 of Figure 2,

Figure 11 is a perspective view on a reduced scale showing a known type of mortar with the improved sight attached thereto.

Referring in detail to the drawing, B indicates the barrel of a mortar which as shown at Figure 11 may have the usual base plate P, traversing mechanism T, and elevating mechanism E carried by bipod S.

As shown at Figure 2, a split clamping band l has its ends turned outwardly to form lugs 2 and 3 which are apertured to receive a pair of clamping bolts 4 and 5. These bolts are suthciently long to receive sections of tubing 6 and l in order to locate Wing nuts 8 and 9, threaded on the readapted to be embraced by a retaining spring` member I3.

Member I3 is best shown at Figure 9 where it l will be noted to comprise a base plate I4 notched as at I5. The end of plate I4 Opposite notch I5 has an elongated narrow integral 'projection bent back upon itself at IS to form a latch member I1 having its nose offset toward base plate' i I4. The bracket proper comprises two parts, the first of which is shown at Figure 8 as being formed of a iiat sheet I9 having its top and bottom sides bent over on itself to form upperand lower guideways or channels 2l] and 2|. In addition a projection at one end is bent outwardly to form a stop lug 22 lying between the channels 20 and 2l. Portion I8, plate I4, and sheet I 9 are formed with holes, shown as four in number in each case. Corresponding holesv ,are in Valignment when the aforesaid parts are in proper contacting relation. Rivets passing through these holes secure parts I0, I3 and I9 in fixed rigid relation so that, when band I is in clamped position encircling the barrel of the mortar channels 2li and 2l are parallel to the axis `of the mortar bore. As shown .at Figure'Z, arcuate end I I of bracketsupport I0, may havean .offset portion to form, with band. I, an eye 23 pivotally accommodating a carrying ring 24.

The quadrant is best shownupon Figures 1 and 2, and includes a sector-shaped plate 25 having its radial boundary edges at somewhat more than 90 to Veach other. The arcuate edge is pressed laterally (Fig. 4) to form a rim26 then out wardly to form a reinforcing flange 21..' A scale plate 28, Vgraduatedfrorn zero to approximately 110 in steps of 1, is secured to the outer surface of rim 26 by means .of cap screws 29. It will be noted from Figure 1 that the radius extending from the center of the quadrant to the zero graduation on scaler 28, is parallel to the axis of the mortar bore when the sight is properly mounted. An arcuate slot 30 in quadrant 25 is concentric of and adjacent to rim.28. This slot is substantallycoextensive withl the graduations upon scale plate 28. A hole 43, Figure 4, is formed at the center of theY quadrant about which arcuate rim 25 and slot3 are concentric and radially extending depressions are struckoutwardly in the plate, as shown atl 3|. In the arrangement shown, depressions spaced at 1 intervals extend between the outer edge of slot 36 and rim 23. These also extend for equal, relatively short distances radially .inwardly from the inner edge of slot 30 while as shown at 32, Figure 1, every fifth depression, -thatris, atV 0, 5, 10 etc., is longerthan the intervening ones, for a purpose to be subsequently described,

Figure 1 shows the second part 33 of the mounting bracket, that is, the part secured to quadrant 25.4 This part is formed from a flat sheet having its upper and lower edges struck at right angles to its plane as at 34 and then outwardly to forni offset guides adapted to have a smooth sliding iit within'cha'nnels 20 .and 2I. At one end, part 33 has a stop lug 36 struck outwardly to extend between the portions 34 and of a Width suiilcient to engage lug 22 and thus limit the K sliding of pa'rt`33 on par-t I9 tol positively locate il I) the two parts in proper relation. At the other end, bracket part 33 is struck laterally between portions 34, to form a second stop lug 31 which is of a width suicient to engage the adjacent end of sheet I5 when the two parts of the bracket are fully engaged with guides 35 'engaged within the respective channels 23 and 2|. From Figure iv it will be noted that, when the parts are in the aforesaid fully engaged position, the latch I1 of spring I3 engages over the end of lug 31 and preventsv separation of the bracket parts unlessand until the latch is manually depressed. `Figures 4 and 'Tshcw that lugs 3B and 31 differ in width by approximately the thickness of sheet I9. `Four attaching-holes 38 are provided in part 33. Four depressions 39 are stamped in quadrant 25. Each depression has an aperture in its base so that when the quadrant and bracket part 33 are in proper relation, the respective pairs of holes are in alignment. Rivets 43 pass through each pair of aligned holesto secure. the parts rigidly together and, because of the depressions 39, said parts are in spaced parallel relation.

The sight arm comprises a base portion 4I of generally right augular L`shape having a pivot hole adjacent the apex. A bolt 42extends through this hole and hole 4.3 in quadrant 25, to pivotally mount portion 4I upon the quadrant. The lower part of 4i extends radially of pivot 42 and has its outer edge 44 in vsubstantial coincidence with the arcuate edge vof the quadrant. A projection 45 shown as integral with the base portion 4|, extends beyond this edge and has its pointed end bent Yinwardly to extend over and closely adjacent scale plate 28 and thereby form an indicator 43 cooperating with said plate. In this way, an indication of the angularrelation of the line of sight to the'quadrant isafforded from a point such that it may beseen'by the operator looking along the line of sight'and substantially without movement of his head. As shown at Figure 5, the inner surface of base 4I extending over the alternate radial depressions and ridges on quadrant 25 has corresponding' radial de# pressions and ridges formed at 1 spacing. Thus when the two serrated portions are drawn into engagement by turning Adown locking nut 41, the arm is thereby positively held inV its position of adjustment. TheV aforesaid lower portion is bent slightly outwardly along a line indicated at AA, Figure 1, so that when nut 41 is loosened, the bent portion moves to separate its teeth from those on the quadrant. The clamp bolt 48 passes through slot 39, anda holer in base 4I. A spring washer 49 is interposed between thehead oi the bolt and the quadrant. The nut 41 has a radial ridge on its pressure face which is adapted, in two positions of the nut ier each rotation, to engage within a depression formed in base 4I. In this manner the spring washer acts to urge the ridge into the depression while preventing loosening of the nut by recoil and shocks engendered by firing of the mortar. At the same time, the teeth onquadrant 25 and base 4I, are firmly held in engagement. If desired, the bolt 48 may have its head secured to quadrant 25 either directly or through resilient dished Washer 43.

Asbest shown upon Figures 1, 3 and 1l, the base 4I has a pair of holes formed therein. One hole is located so that, upon pivotal movement of the Ysight about pivot 42, it moves over and along the 1 depressions on the quadrant. |This hole is ci a size to snugly receive a ball 5E! urged inwardly into contact with the`1 depressions by a leaf spring 5I held in superposed postioncver the ball by a pair of screws 52 threaded into the sight base 4|. A second ball 53 fits snugly into a hole in -base 4i and is so positioned as to move over and across the 5 depressions 32 only. A leaf spring 54 is held to base si' by screws 55 and acts to urge the ball into each 5 radial depression as it passes thereover during pivotal movement of the sight. The arrangement and relation of the parts are such that, for example, when the line of sight is at 15 to the axis of the mortar bore, both balls 50 and 53 lie in a depression while, when the line of sight is at an angle other than 5 or a multiple thereof, only ball 5U lies in a depression. Thus, as the sight and its base are pivoted, a click will be heard and a yielding resistance felt for each degree of angular movement thereof, while for each fifth degree a louder click will -be heard and increased resistance will be felt. Thus it is possible, by noting and counting the clicks or resistances, to quickly and accurately adjust the sight to any angle within its range of movement. For example, if a 47 angle of adjustment is called for, the operator, starting with the sight at elevation, will note and count nine clicks and/or resistances, followed by two 1 clicks or resistances. He will then know that the sight line is at 47 to the axis of the bore. Adjustments are thus possible in the dark or at any other time, without looking at the scale and pointer. In so counting or noting resistances, the one felt when ball 50 moves out of the 0 position is, of course, ignored.

The base 4l has a triangular-shaped area struck outwardly as indicated at 55, Figures l, 2, 3 and 6. The sight proper has a correspondinglyshaped depending fiange 51 secured to raised portion 56 by three screws 58. The sight is bent outwardly along a line substantially coincident with the top edge of base 4i to form a platform 59 for the support of a circular bubble level or viai ii. As shown upon Figure 10, this vial consists of a casing 60 secured to platform 59 by screws 6i A vial 62 fits, and is secured within casing (iii by the inwardly-hanged upper edge thereof. The vial itself may comprise a container of transparent material having its upper surface formed as a portion of a sphere and filled with liquid 53 and an air bubble 64.

The platform 59 has its ends turned upwardly at 90 to form risers B5 and 85 which are again turned outwardly at about the level of the top of casing 6D, as indicated at 61 and E5. Figure l. The forward end of extension 5'! is bent upwardly to form a forward sight 69 tapered at the top to form a sighting point 16. The rearward extension 68 is provided with a transverse slot 'H through which extend a pair of screws i2 into threaded engagement with a rear sight 'i3 including a forward flange 'iii engaging riser 55, and a rear upstanding portion which, as shown at Figure 2, has a sighting point or notch T5 in its upper edge, and an observation aperture 'H below notch 16. When the sight is attached to the mortar barrel and the parts are in the positions of adjustment shown at Figure l, the line of sight determined by sighting elements '15, 'i6 is parallel to the axis of the bore of barrel B and the indicator 48 is at the zero graduation of scale 23, as shown upon Figure 2.

A mirror bracket 18 has its base longitudinally slotted. Screws '19 nass through this slot to adjustablv secure the bracket to extension El. The bracket has its rear end bent upwardly at 45 to the plane of its base, and apertured to receive a bolt 80 secured to the base 8i of a mirror 32. See

Figure 10. The base 8| and mirror 82 may conveniently be circular in section and united by spinning the top edge of the |base over the edge of the mirror, as indicated at 83. It will be noted that the base 8l is rounded at its uppermost portion so that it does not obstruct the line of sight. The mirror is adjusted by loosening screws "i9, and shifting the bracket longitudinally until the reection of bubble G4 can be seen lby the observer when looking through aperture Ti. The sight elements 1G, i6, as well as the markings of scale 2B and pointer 45 may, if desired, be coated with luminous material to thereby facilitate the use of the instrument at night. The bent portions of the sight may be rigidified by pressing or striking up reinforcements, as indicated, for example, at 85, Figures 1, 3 and 4.

In operation, the elevation angle necessary to hit a target will be determined by the battery commander and conveyed to the mortar station by any available means. Likewise a visible aiming point will ibe designated. This may be the target itself if visible from the mortar emplacement or, as is more likely to ibe the case, an aiming point in the line between the mortar and concealed target. With the mortar properly placed to re in the general direction of the target and band i properly clamped in place on the mortar barrel, the quadrant sight and bracket part 33 are positioned by sliding portions 35 within channels 2B and 2| until the nose of latchl member i1 snaps over lug Si'. The designated member of the crew next loosens nut ii and either by sense of touch or hearing, as previously described, or Iby direct observation of pointer 15, depresses the sight arm until the line of sight makes the desired angle with the bore axis. Nut i1 is tightened and the mortar is elevated by operating mechanism E, Figure 11, while the aforesaid crew member continuously looks along the line of sight With his eye at l5. Without any substantial movement of his head, he may glance through aperture 'Vi and note the position of bubble 64 as disclosed by its image in mirror 82. When he notes that bubble is properly centered; he gives the proper signal to stop further elevation. The line of sight is now horizontal and the mortar is traversed by operating mechanism .T until the line of sight is directed upon the previously-identified aiming point. A final check is made to make sure that the bubble @d is properly centered. The mortar is now ready for firing.

It should be noted that if at any time the bubble moves laterally due, for example, to uneven subsidence of the motar supports during firing, correction can be made simply by loosening nuts 8 and 9 and shifting the entire sight about the axis of the barrel until the bubble is again laterally centralized. The nuts are then tightened and the mortar train and elevation are changed as necessary, without changing the adjustment of the sight relatively to quadrant 25, to restore the line of sight to the aiming point. Errors otherwise introduced by the aforesaid uneven subsidence are thus compensated, the action being in all respects similar to the cross-leveling correction commonly applied to guns and hovvitzers.

From the foregoing description, it Will be seen that We have provided a mortar sight that is relatively simple and easy to construct and repair, while at the same time quickly attachable. Elevation adjustment is determinable either by sight, hearing or touch and-all adjustments are positively maintained during firing until the'4 necessity for a change is indicated by bubble 64. Cross leveling corrections which may be made necessary by uneven subsidence of the mortar supports are easily introduced and are geometrically accurate. Finally, one man is enabled to determine the position of the line of sight relatively to the gun and, at the same time, to determine when the line of sight is horizontal and properly directed to the aiming'point or target.

While we have used the term depression in identifying the graduations 3| and 32, it will be understood that these may be projections or ridges and that the detents may comprise notched elements adapted to snap over the successive projections or ridges as the sight arm is rotated. It is our desire therefore, that the term depression as used in the speciflcation and claims shall be interpreted, to include modications employing ridges or teeth in the sense just deiined.

While we have shown the form of the invention now preferred by us, modilications and substitutions of equivalents will be obvious to those skilled in the art. It is our desire to reserve all those changes that fall within the scope of the subjoined claims. Hence the foregoing description should be taken in an illustrative, rather thanva limiting sense.

Having now fully disclosed our invention what we claim and desire to secure by Letters Patent is:

1. In a sight for mortars, a clamping band adapted to encircle the mortar barrel, a iirst bracket part carried by Vsaid band, a second bracket part, a quadrant iixed to said second part, a sight pivoted on said quadrant on a first axis normal thereto, and means carried by said first and second parts and adapting the same for interconnection by a translational movement in a direction parallel to the axis of the bore of said mortar barrel when said bandV is in position thereabout, said direction also being normal to said rst axis.

2. A sight for mortars comprising clamp means adapted to be affixed to the mortar barrel, a first bracket part carried by said clamp means and forming confronting channels parallel to the axis of the bore of said mortar when said clamp means is in proper position thereon, a second bracket part having guide portions receivable within the respective channels, stop means carried by said parts to engage when said parts are in assembled relation, latch means carried by said clamp means and adapted to engage over the end o-f said second part when the same is fully engaged with said rst part to render said stop means eiective, a quadrant carried by said second part, and having a scale concentric about a second axis normal to the axis of said bore, and sighting means pivoted on said quadrant on said second axis and having indicating means movable over said scale to indicate the angular relation between the line of sight determined thereby and the said axis of said bore.

3. A sight for mortars comprising a first bracket part consisting of a flat plate having its opposite edges bent over on itself to form parallel guide channels and having one end bent upwardly between said channels to form a first stop, a second bracket part consisting of a plate having its opposite side edges offset to form guides receivable in said channels, respectively, by relative translation of said parts in a first direction parallel to said channels, said second part having one end edge bent downwardly between said offset edges to form a second Vstop engageable with said first stop and having its other end edge bent downwardly between said odset edges to engage the other end edge of said rst part when said stops are in engagement, latch means ilxed to said rst part and adapted to engage said second part when said parts are fully engaged, a quadrant carried by said second bracket part and having a scale of angles concentric of an axis normal to said iirst direction, a sight pivoted on said Vquadrant on said axis and having indicating means cooperative with said scale, and clamp means adapted to attach said rst bracket part to the barrel of a mortar with said channels parallel to the axis of the bore thereof.

4. In a sight for a gun, a sector adapted to be attached to said gun, said sector having scale means thereon, said scale means comprising rst and second concentric rows each said row comprising regularly-spaced depressions extending radially of a pivot axis, the spacing of the depressions of said second Vrow being a iixed multiple of the depressions of said iirst row, a sight arm pivoted on said sector on said axis and first and second yielding detent means carried by said sector, each detent means being adapted to engage the depressions of a respective row.

5. In an elevation sight for a gun, a quadrant adapted to be mounted upon said gun, said quadrant having arcuate scale means thereon concentric of an axis, said scale means including rst and second rows of regularly-spaced depressions concentric of said axis, the depressions of said second row being spaced at intervals equal to a xed multiple of the spacing of the depressions of said iirst row, a sight arm pivoted on said quadrant on said axis, and iirst and second resilient detent means carried by said arm, each said detent meansn being positioned to successively engage the depressions of a respective row as said arm is pivoted, the arrangement being such that when said second detent means is engaged with a depression of said second row, said rst detent means engages a corresponding depression of said first row, whereby the said arm' sions of said second row being a predetermined' multiple of the spacing of the depressions of said first row, a sight arm pivoted upon said pin, rst and second resilient detent means carried by said arm, each said detent means being positioned to move over and successively engage the depressions of said first and second rows as said arm is pivoted, there being a plurality of projections on the under side of said arm each adapted to engage a depression of said iirst row in all adjusted positions of said armand clamping' bolt means passing through said slot and an aligned hole in said arm and operable to force the teeth on said arm into the depressions of said first row.

7. In a sight for a mortar, a quadrant plateV having bolt means defining an axis normal to said plate, a sight arm pivoted on ,said bolt means,

said arm including a normally horizontal plat-V form, and iirst and second extensions extending grasse forwardly and rearwardly therefrom parallel to said plate, a fore sight carried by the forward end of saidrst extension, a vnotched rear sight carried by the rearward end of said second extension, a level mounted on said platform between said sights and laterally oifset from the line of sight determined thereby, there being a viewing aperture in said rear sight vimmediately adjacent the sighting notch therein, a mirror carried by said platform and disposed to reiiect an image of said level through said aperture, and means adapted to detachably mount said plate upon the mortar.

8. A sight for mortars comprising a quadrant plate having pivot means dening an axis normal to said plate, first and second rows of depressions carried by said plate, each row being concentric of said axis, the spacing of the depressions of said second row being a predetermined multiple of the spacing of the depressions of said rst row, a sight arm pivoted upon said pivot means, first and second detent means on said arm, each detent means adapted and positioned to successively engage the depressions of a respective row as said arm is rotated, said second detent means engaging within a depression of its row simultaneously with the engagement of said first detent means with a corresponding depression of its row, whereby said arm may be adjusted by touch in steps equal to said multiple or to the depression spacing of said iirst row.

9. A sight for mortars comprising a sectorshaped plate having a pivot means defining an axis and a rim offset from the plane of said plate and concentric of said axis, a scale of Aangular measures carried by said rim, a sight arm on said pivot means and having a pointer extending closely adjacent said rim for coaction therewith, said arm including a platform having a plane surface parallel to said axis and the radius from said axis to pointer, said arm also including forward and rearward extensions from said platform and having respective fore and rear sights at their ends, said sights cooperating to dene a line of sight parallel to said plate, a bubble level on said platform adjacent said line of sight, a mirror carried by said arm in position to reiiect an image of the bubble thereof to a position closely adjacent said rear sight, the arrangement being such that an observer locking along said line of sight from said rear sight is able to view said pointer and the image of said bubble, without moving his head.

10. A sight arm for gun sights comprising a base portion, an oiset platform carried by said base portion, a first extension extending upwardly then forwardly from the front edge of said platform, a second extension extending upwardly, then rearwardly from the rear edge of said platform, said first extension having an upwardlyextending fore sight at its forward end, said second extension having a rear upstanding plate having a sighting aperture cooperating with said fore sight to determine a line of sight and a viewing aperture beneath said sighting aperture, a bubble level on said platform, a mirror bracket on said rst extension, and a mirror carried by said bracket below said line of sight and reflecting an image of said level through said viewing aperture.

11. In a sight for guns, a sighting arm including a platform, substantially coplanar forward and rearward extensions carried by said platform above the plane of said platform, fore and rear sights carried by the respective extensions and determining in cooperation,- aline of sight substantially parallel togandabove said platform, a bubble levelon saidj platform, a bracket on said forward extension, and a mirror on said bracket below said line of sight and positioned over said level to projectv an image of said level toa Yposition closely adjacent said rear sight.

12. A sight for mortars comprising a` quadrant having a pivot axisnormalto said quadrant and a scale of angular values concentric of said'axis, a sight arm pivoted on said axis including 'fore andr'ear sights determining a line of sight parallel to Said quadrant and a pointer movable over said scale as said armv is pivoted, andidetent means betwee'nsaid arm and quadrant and eifective to give one signal for a unit movement of said arm and a second signal diiering from said iirst signal for a movement of said arm equal to a predetermined multiple of said unit movement.

13. A sight for a mortar comprising a quadrant having a scale concentric of a pivot axis thereon, a sight arm pivoted on said axis and havingsighting means determining a line of sight parallel to said quadrant, indicator means on said arm cooperating with said scale to indicate the angular adjustment of said line of sight relatively to said quadrant, a first bracket part having spaced parallel guide channels, a second bracket part secured to said quadrant and having offset anges slidably fitting said channels, respectively, stops carried by said bracket parts and engageable to limit sliding movement between them, a band adapted to be clamped about the barrel of said mortar and having an oifset supporting plate, a U-shaped spring member having its legs embracing said plate, means securing said first bracket part, plate and one leg of said spring member rigidly together, and a latch on the free end of the other leg of said spring member and adapted to engage and releasably lock said second bracket part when said stops are in engagement.

14. In a mortar sight, a clamping band adapted to encircle the barrel of a mortar, and having a supporting plate xed thereto in radially offset position parallel to the central axis of said band, a U-shaped spring member embracing said plate, a first bracket part, means securing said part, and a first leg of said spring member rigidly together as a unit, guide means on said rst bracket part dening a path parallel to said central axis, the free end of the second leg of said spring member having a latch yieldingly urged thereby into said path, a second bracket part having means engageable in and slidable along said guide means in said path, a quadrant xed to said second bracket part, a sight arm pivoted on said quadrant, and stops carried by the respective bracket parts and engageable to limit relative sliding of said parts along said path, said latch being engageable with said second bracket part tc releasaby prevent reverse sliding of said second part when said stops are in engagement.

l5. In a sight for a gun, a sector adapted to be attached to a gun, a scale on said sector, said scale comprising a plurality of regularly-spaced depressions each extending radially of a pivot point, each nth depression being longer than the interposed remaining depressions, n being an integer greater than one, a sight pivoted on an axis intersecting said point and having a portion movable over said scale, and first and second detents carried by said portion, said rst detent being adapted to successively engage each said depression and said second detent being adapted il I12 torle'nggg egch 11@ niigepvlgssion only, Vas said Y n FOREIGN PATENTS sight is pivoted about gai@ #511 Number Gauntry Y Date.

IQHNfEf-HRB'JF' 55o Great Britain 11. 111896 U; MATSON.

111,171 Australia u1-1.1--;1.- A. 13i 1939 Pages 10 ad 11, aim piaf@ 4, of dbol: No;

1745, ntitled, Handkook of the 6 Irl-@11 Tfn 

